Method for producing a hydrocarbon-containing formation

ABSTRACT

A hydrocarbon-containing formation penetrated by at least one in-jection well and at least one producing well is produced by passing flooding fluid at a preselected rate into the formation via the injection well while transmitting oscillatory pressure waves from the injection well outwardly through the formation for forming a wave zone in the formation and moving the wave zone outwardly through the formation by altering at least one of the frequency or amplitude of the oscillatory pressure wave transmissions.

OOOOO 11:1 States Patent [191 [111 3,754,598 Holloway, Jr. Aug. 28, 1973 [54] METHOD FOR PRODUCING A 2,670,801 3/1354 SherbornIe 166/249 HYDROCARBON CONTAINING 2,700,422 1 l 55 Bodme, r... 166/249 FORMATION 2,871,944 2/ 1959 Pleuger 166/249 3,322,196 5/1967 Bodine, Jr... 166/249 [75] lnventor: Carl C. Holloway, Jr., Bartlesville, 3,520,362 7/1970 Galle 166/2491 0k|a 3,578,081 5/1971 Bodlne 166/249 [73] Assign: gg g 33 Company Primary Examiner-Stephen J. Novosad as Attorney-J. Arthur Young et a1. [22] Filed: Nov. 8, 1971 [21] Appl. No.: 196,673 ABSTRACT A hydrocarbon-containing formation penetrated by at 52 us. or 166 249 166 271, 166 275 in'jecfim! and Pmducinfl [511 1111. c1. 13211) 42/22 is Pmduc Passing fluid a 58 Field 61 Search 166/249 268 280 me via the 11mm whik 8 transmitting oscillatory pressure waves from the injection well outwardly through the formation for forming [56] References Cited a wave zone in the formation and moving the wave zone outwardly through the formation by altering at 3 323 592 Z Z PATENTS 166/249 least one of the frequency or amplitude of the oscillaran on t n- 2,792,894 5/1957 Graham et a] 166/274 X ory pressure wave ansmmslons 3,302,713 2/1967 Aheam et 166/275 X 6 Claims, 6 Drawing Figures FLOOD FLO) FLOOD ADDITIVE Patented Aug. 28, 1973 2 Sheets-Sheet l O O O O O O O O O O 05 4" OOO E INVENTOR. (LC. HOLLOWAY 2 Q ATTORNEYS METHOD FOR PRODUCING A HYDROCARBON-CONTAINING FORMATION It is desirable to provide methods for more efficiently recovering hydrocarbons from a subterranean hydrocarbon-containing formation. A multiplicity of methods have been discovered for improving the recovery efficiency yet large volumes of hydrocarbons remain in the formation after secondary and tertiary recovery methods have been practiced. It is believed that the major factor causing the retention of the hydrocarbons in the formation is the heretofore inability to direct sufficient pressure forces on the hydrocarbon droplets residing in the pore spaces of the formation matrix.

In summary, this invention resides in passing flooding fluid through the hydrocarbon-containing formation, transmitting oscillatory pressure waves outwardly through the formation while injecting the flooding fluid forming a wave zone and moving the wave zone through the formation in a direction toward a producing well by altering at least one of the frequency or amplitude of the oscillatory pressure wave transmissions.

Other aspects, objects, and advantages of the present invention will become apparent from a study of the disclosure, the appended claims, and the drawings.

The drawings are diagrammatic views of the formation and equipment utilized in the practice of this invention.

FIG. 1 shows the hydrocarbon-containing formation, injection well, and associated wave transmitter and the production well,

FIG. 2-5 shows the formation with the wave transmitter positioned at different locations and FIG. 6 shows the formation and an injection well and a producing well each with associated wave transmitters.

Referring to FIG. 1, an injection well 2 and a production well 4 extend from the surface through a subterranean hydrocarbon-containing formation 6. Here the wells 2, 4 are completed having their casing set through the formation as known in the art. It should be understood that this type of completion is for illustration purposes only and the invention can be practiced in any well irrespective of the way in which said well was completed.

As also known in the art, the injection well 2 is equipped for passing flooding fluid from the surface downwardly through the well and into the hydrocarbon-containing formation 6. Means are also preferably provided for adding flooding fluid additives or fluids to the flooding fluid.

Further, as known in the art, the production well 4 is equipped for producing and recovering fluids entering the production well 4.

An oscillatory pressure wave transmitter 8, such as shown in U. S. Pat. No. 3,520,362 or other apparatus for providing pressure waves of substantially sinusoidal configuration, is positioned adjacent the formation 6. In the embodiment shown in FIG. 1, the transmitter 8 is associated with the injection well 2. As further shown in FIG. 6, a transmitter 8 can also be associated with a production well 4 as hereafter more fully described.

Referring to FIGS. l-5, the transmitter 8 can be positioned at various positions relative to the hydrocarboncontaining formation 6 for altering the producing method of this invention. FIGS. 1 and 2 show the trans: mitter 8 positioned adjacent a middle portion 10 of the fonnation 6, FIG. 3 shows the transmitter 8 positioned adjacent a lower portion 12 of said formation 6, FIG. 4 shows the transmitter 8 positioned adjacent an upper portion 14 of the formation, and FIG. 5 shows the transmitter 8 positioned at a common elevation relative to the opening 16 of a fracture 18 extending through the formation 6.

It should be understood that the transmitter 8 can be positioned at other locations relative to the fracture l8 and that the fracture 18 can be positioned at other locations relative to the thickness of the formation 6. It should also be understood that where a transmitter 8 is desired with the production well 4, that said transmitter can be also positioned at different locations relative to the thickness of the formation 6.

In the method of this invention, a flooding fluid is passed downwardly through the injection well 2 and outwardly to the formation 6 for sweeping hydrocarbons from the formation into the production well 4 for recovery therefrom, as known in the art. The injection rate of the flooding fluid is dependent upon the formation thickness, porosity, penneability, etc. and is a value that is routinely calculated or selected by one skilled in the art.

During injection of the flooding fluid, oscillatory pressure waves are transmitted from the injection well 2 outwardly through the formation 6. These oscillatory pressure waves are of a general sinusoidal configuration and have a preselected amplitude in the range of about 10 to 5,000 psi above the reservoir pressure and a frequency in the range of about 0.001 to about 25 cycles per second for forming a pressure wave zone 20 in the formation 6 about the injection well 2.

The pressure waves passing through the formation 6 causes a fluid positioned within the pore spaces of the matrix to be forced therefrom for subsequent removal through the formation 6 and into the production well 4 for recovery.

The recovery of hydrocarbons from pore spaces of the formation depend on the ratio of the imposed pressure gradient to the tension forces acting on the hydrocarbons. This tension force can be the interfacial tension between oil and water where the formation is termed water-wet, tension between the oil and the matrix where the formation is termed oil-wet for example and as known in the art.

The higher the ratio, the greater the oil recovery. However, overburden pressure, fracturing pressure characteristics of the fonnation, and other factors known in the art limit the upper pressure that can be applied while substantially uniformly continuously exerting a pressure. The ratio however can be increased by establishing a high pressure gradient momentarily by repeated pressure oscillations while maintaining a preselected net flow through the formation 6.

Further, slugs of surfactant material, such as Bryton 430, alkali metal (Na,K,Li) salts of petroleum sulfonates, manufactured by Bryton Chemical Co. Park Eighty Plaza East, Saddle Brook, N.J.; Pluronic L64, condensate of ethylene oxide with hydrophobic bases, manufactured by BASF Wyandotte, Corp., Industrial Chemicals Group, Wyandotte, Mich.; Igepal CO530, nonylphenoxpoly(ethyleneoxy) ethanol, manufactured by General Aniline & Film Corp., West 51st, New York, N. Y.; Aerosol OT, Na dioctyl sulfosuccinate, manufactured by American Cyanamide, Berdan Ave., Wayne, N.J.; and the like can be added to the flooding fluid and passed into the formation 6. This surfactant 22 further facilitates increasing the ratio by lowering the tension forces acting on the in-place hydrocarbons.

As the sinusoidal pressure wave travels through a porous medium at a velocity V,,, the pressure gradient at the front of the wave is related to the frequency and the amplitude of the oscillations. The higher the frequency or the greater the amplitude, the greater the pressure gradient. Also, the' pressure amplitude at any radial point from the injection well decreases as the frequency increases. The pressure gradient at any radial point increases as the frequency increases becausethe effect of shortening the wave length is greater than the dampening of the pressure. These facts are numerically shown by Tables I and II as follows:

TABLE 1" [Pressure (D.s.i.) vs. radius (velocity of propagation=250 it./sec.)]

Frequency (c.p.s.)

Radius (It) Static 0010 016 16 1. 6 16 160 60. 6 55. (i 40. 2 26. (i 22. 6 22. 3 22. 3 51. 5 46.0 29. 9 18. 8 15. .l 15. 8 15. 3 46. 1 40. 6 24. 8 15. 3 13. 12. 9 12. 9 42.4 36.9 21.7 13.3 11.2 11.1 11.1 37. 0 31. 9 17. 8 10. 3 9. 2 .1. 1 9. 1 33. 2 28. 6 15. 4 9. 3 7. 9 7. 8 7. 8 30.3 26.1 13.8 8.3 7.1 7. 0 7. 0 25.0 21.7 11.1 6.7 5.7 5.6 5. 6 2.2 18.9 9.5 5.7 4.9 4.8 4.8 18. 2 17. 0 8. 4 5. 1 4. 3 4. 3 I. 3 15. 8 15. 5 7. t) 4. f1 3. 9 3. 9 9 13. 8 14. 2 7. 0 4. 2 3. ti 3. 5 3. 5 12. l 13. 3 6. 5 3. 9 3. 3 3. 3 3. 3 10. 5 12.4 6.1 3.7 3. 1 3.1 3.1

TABLE 11 [Pressure gradient (psi/ft.) psi ragllius (Velocity of propagati0n=250 t. sec.

Frequency (c.p.s.)

Radius (ft.) Static .0016 .016 16 1. 6 16 160 500 026 056 O. 26 1. 0 13 132 1, 317 Required for snap-off 189 1. 89 18. 9 189 1,890 18, 900

It has been discovered that a droplet of oil of a diam eter 7 times the pore neck radius must form before that droplet can be snapped-off or separated from association with its pore situs. This snap-off occurs during the positive pressure gradient portion of the cycle and conversely the oil droplet moves back into the pore situs during the negative gradient portion of the cycle. After snap-off of a droplet, that droplet is moved through the formation by the flow of flooding fluid through the formation.

As more fully shown in the example, one skilled in the art can calculate the minimum pressure gradient required for snap-off for certain formation characteristics. These calculations will also disclose the radial extent to which this pressure gradient extends from the transmitter 8.

Therefore, after the hydrocarbons have been snapped-off from their situs to the radial extent of the minimum pressure gradient and these snap-off droplets have been moved toward the production well 4 by the flooding fluid, the wave zone is moved through the formation in a direction from the injection well toward the producing well to snap-off and remove hydrocarbon droplets at other portions of the formation 6, thereby sweeping the formation pores of in-placc hydrocar bons. This wave front is caused to move outwardly from the injection well to greater areal extents by altering at least one of the frequency or amplitude of the oscillatory pressure wave transmissions. The frequency can be decreased, the amplitude increased, or a combination of the two will cause said outward movement of the wave zone 20.

By so passing the wave zone 20 through the formation in conjunction with the flooding fluid passing therethrough, the formation 4 can be more efficiently cleaned of in-place hydrocarbons.

A surfactant slug or multiplicity of slugs can be injected as shown in FIGS. 2 and 3 for increasing the hydrocarbon recovery as set forth above. As known, as a volume of the surfactant passes through the formation, said volume decreases.

The porosity, permeability and pore space distribution can change from one formation to another and problems associated with effectively moving hydrocarbons therethrough can be eliminated by differing the placement of the transmitter 8 relative to the formation thickness and existing fractures 18 through the formation 6. Where a fractured formation is to be subjected to the method of this invention, it is preferred that said fracture be fractured utilizing an in situ form popcorn polymer plugging agent as set forth in U. S. Pat. No. 3,608,639. Use ofa popcorn polymer plugging element eliminates any problem of shifting of the propping agent by the effect of the imposed pressure gradients. FIG. 2 shows the transmitter 8 placed in the middle portion 10 of the formation, FIG. 3 shows the transmitter 8 in the lower portion 12 and FIG. 4 shows the transmitter 8 in the upper portion 14. Core and log analysis will give an indication of the general direction in which the flooding fluid will move through the formation. The pressure waves preferably are directed in the general direction of this fluid flow to increase the efficiency and effect of the pressure oscillations. Accordingly, the transmitter 8 is positioned relative to a fracture 18 as shown in FIG. 5.

Where the formation 6 adjacent the production well 4 becomes partially plugged by foam, mud, emulsion, or other items known in the art, a transmitter can be positioned in the producing well and operated to at least intermittently transmit oscillatory pressure waves through the formation to move material from their situs.

The transmitted pressure waves can also be composite waves where the major wave is of a general sinusoidal configuration being sinusoidal variations of lesser magnitude along at least a portion of the length of the major wave. One example would be to have sinusoidal variations of lesser magnitude during the period when said major wave is moving in a positive direction.

The following is an example of the calculations and description for producing a formation by the method of this invention.

EXAMPLE Tables I and II are for a 500 md formation having a porosity of 26 percent with the flooding being water of specific weight 62.4 lb/ft and viscosity of 0.71 cp. The values of pressure and pressure gradient shown in The Table are due to oscillatory pressure only, and the velocity of propagation of the pressure pulses is assumed to be 250 ft/sec.

The pore size distribution for this formation as determined by the mercury porosimeter method on a core sample shows the minimum pore size to be 0.01 microns, the maximum pore size of 100 microns and the median pore size of microns.

Calculation of the minimum pressure gradient required for snap-off is as follows. Darcys law for the fluid flow rate is q r p/ where q flow rate (cm /sec) cross section area (both rock and pores) (cm k permeability (darcy) u viscosity (cp) dp/dx pressure gradient (atm/cm) The flow rate through the cross-sectional area of pores only is v b P/ where A,, cross-sectional area of pores only (cm') (I) porosity The rate of oil flow through a pore of radius r is At a frequency of N cycles per second the time in which flow can occur is 1/(2N) seconds so the volumetric flow is Q( (Wrk/ 4 i Imposing the condition for snap-off.

(1rr k/2Nu) (dp/dx) z (1r/ U Solving for the required pressure gradient dp/dx) 2 (R uN/k) [(7)'"'13](atm/cm) For r=l0 microns, the pressure gradient required for snap-off is dp/dx z 18.9N (psi/ft.)

The minimum required pressure gradient for snap-off is shown on Table II.

Other modifications and alterations of this invention will become apparent to those skilled in the art from the foregoing discussion, example, and accompanying drawings, and it should be understood that this invention is not to be unduly limited thereto.

What is claimed is:

l. A method for producing hydrocarbon fluids from a subterranean hydrocarbon-containing formation penetrated by at least one injection well and at least one production well spaced from said injection well, said injection well passing flooding fluid from the surface into the subterranean hydrocarbon-containing formation at a preselected rate and with fluid entering the production well being passed to the surface, compris' ing:

transmitting oscillatory pressure waves from the injection well outwardly through the formation while injecting the flooding fluid, said oscillatory pres sure waves having a preselected amplitude in the range of about 10 to about 5,000 psi above the reservoir pressure and a frequency in the range of about 0.001 to about 25 cycles per second for forming a wave zone in the formation about the injection well;

transmitting oscillatory pressure waves at least intermittently from the producing well outwardly through the formation; and

moving the wave zone through the formation in a direction from the injection well toward the production well by altering at least one of the frequency or amplitude of the oscillatory pressure wave transmissions.

2. A method for producing hydrocarbon fluids from a subterranean hydrocarbon-containing formation penetrated by at least one injection well and at least one production well spaced from said injection well, said injection well passing flooding fluid from the surface into the subterranean hydrocarbon-containing formation at a preselected rate and with fluid entering the production well being passed to the surface, comprising:

transmitting oscillatory pressure waves from the injection well outwardly through the formation while injecting the flooding fluid, said oscillatory pressure waves having a preselected amplitude in the range of about 10 to about 5,000 psi above the reservoir pressure and a frequency in the range of about 0.00] to about 25 cycles per second for forming a wave zone in the formation about the injection well, said pressure waves being transmitted into the hydrocarbon-containing formation at a location having a substantially common elevation relative to the opening of a fracture extending through said formation; and

moving the wave zone through the formation in a direction from the injection well toward the production well by altering at least one of the frequency or amplitude of the oscillatory pressure wave transmissions.

3. A method, as set forth in claim 2, including adding surfactant material to the flooding fluid.

4. A method, as set forth in claim 3, wherein the surfactant material is one of an alkali metal salt of petroleum sulfonate, a condensate of ethylene oxide with a hydrophobic base, a nonylphenoxpoly(ethyleneoxy) ethanol, or a Na dioctyl sulfosuccinate, or mixtures 5 thereof.

5. A method, as set forth in claim 2, wherein the fracture has a popcorn polymer propping agent.

6. A method for producing hydrocarbon fluids from ervoir pressure and a frequency in the range of a subterranean hydrocarbon-containing formation penabout 0,001 to about 25 cycles er second for etrated by at least one injection well and at least one f in a wave Zone i the f ti about h production well spaced from said injection well, said jection injection Passing flooding fluid from the surface imparting minor oscillations on the oscillating presinto the subterranean hydrocarbon-containing forma- Sure wave over at least the portion of the wave that tion at a preselected rate and with fluid entering the production well being passed to the surface, comprising:

is increasing in pressure; and moving the wave zone through the formation in a ditransmitting oscillatory pressure waves from the in- 10 rficuon from the n1ecuon toward the produc' jection well outwardly through the formation while well by anenng at least one of the frequency inj tin th fl di fl id id iu m presor amplitude of the oscillatory pressure wave transsure waves having a preselected amplitude in the missionsrange of about 10 to about 5,000 psi above the res- 

1. A method for producing hydrocarbon fluids from a subterranean hydrocarbon-containing formation penetrated by at least one injection well and at least one production well spaced from said injection well, said injection well passing flooding fluid from the surface into the subterranean hydrocarbon-containing formation at a preselected rate and with fluid entering the production well being passed to the surface, comprising: transmitting oscillatory pressure wAves from the injection well outwardly through the formation while injecting the flooding fluid, said oscillatory pressure waves having a preselected amplitude in the range of about 10 to about 5,000 psi above the reservoir pressure and a frequency in the range of about 0.001 to about 25 cycles per second for forming a wave zone in the formation about the injection well; transmitting oscillatory pressure waves at least intermittently from the producing well outwardly through the formation; and moving the wave zone through the formation in a direction from the injection well toward the production well by altering at least one of the frequency or amplitude of the oscillatory pressure wave transmissions.
 2. A method for producing hydrocarbon fluids from a subterranean hydrocarbon-containing formation penetrated by at least one injection well and at least one production well spaced from said injection well, said injection well passing flooding fluid from the surface into the subterranean hydrocarbon-containing formation at a preselected rate and with fluid entering the production well being passed to the surface, comprising: transmitting oscillatory pressure waves from the injection well outwardly through the formation while injecting the flooding fluid, said oscillatory pressure waves having a preselected amplitude in the range of about 10 to about 5,000 psi above the reservoir pressure and a frequency in the range of about 0.001 to about 25 cycles per second for forming a wave zone in the formation about the injection well, said pressure waves being transmitted into the hydrocarbon-containing formation at a location having a substantially common elevation relative to the opening of a fracture extending through said formation; and moving the wave zone through the formation in a direction from the injection well toward the production well by altering at least one of the frequency or amplitude of the oscillatory pressure wave transmissions.
 3. A method, as set forth in claim 2, including adding surfactant material to the flooding fluid.
 4. A method, as set forth in claim 3, wherein the surfactant material is one of an alkali metal salt of petroleum sulfonate, a condensate of ethylene oxide with a hydrophobic base, a nonylphenoxpoly(ethyleneoxy) ethanol, or a Na dioctyl sulfosuccinate, or mixtures thereof.
 5. A method, as set forth in claim 2, wherein the fracture has a popcorn polymer propping agent.
 6. A method for producing hydrocarbon fluids from a subterranean hydrocarbon-containing formation penetrated by at least one injection well and at least one production well spaced from said injection well, said injection well passing flooding fluid from the surface into the subterranean hydrocarbon-containing formation at a preselected rate and with fluid entering the production well being passed to the surface, comprising: transmitting oscillatory pressure waves from the injection well outwardly through the formation while injecting the flooding fluid, said oscillatory pressure waves having a preselected amplitude in the range of about 10 to about 5,000 psi above the reservoir pressure and a frequency in the range of about 0.001 to about 25 cycles per second for forming a wave zone in the formation about the injection well; imparting minor oscillations on the oscillating pressure wave over at least the portion of the wave that is increasing in pressure; and moving the wave zone through the formation in a direction from the injection well toward the production well by altering at least one of the frequency or amplitude of the oscillatory pressure wave transmissions. 